Use of Zeolites as Controlled Release Fertilisers for Hydrocarbon Degradation at Low Temperatures in Antarctica

In coarse-textured soils and gravel pads found in cold regions, hydrocarbon contaminants often migrate into environmentally sensitive areas faster than the rate of in-situ bioremediation. Permeable Reactive Barrier (PRB) technology offers the potential to slow the rate of dispersal and allow remediation over a longer timeframe. Additionally, the reactive media in PRBs can deliver nutrients needed to achieve enhanced biodegradation. A slow release nutrient delivery system offers a number of advantages including; a reduction of the number of nutrient applications required and a reduction in the likelihood of biodegradation suppression associated with osmotic stress through over fertilisation. Following a spill, PRBs can also be used as a rapid response tool to contain dispersal of contaminants in surface and subsurface runoff. This work discusses the implementation and performance of a PRB installed for a fuel spill remediation project at Casey Station, Antarctica. BACKGROUND Casey Station is located on a coastal ice-free rock and gravel peninsula in the Windmill Islands on the coast of east Antarctica (Fig. 1). The spill site under consideration occurred at the Station’s Main Power House (MPH) in July 1999, and was as a result of an overflow of the sump tank from an intermittent fault in the pump control valve. The product spilled consisted of a mixture of Bergen distillate (80%) and Aviation Turbine Kerosene (ATK, 20%). As a result of the leak approximately 2000 tonnes of soil was contaminated with petroleum hydrocarbons (>5000 ppm). K.A. Mumford, I. Snape, G.W. Stevens Fig. 1: Location of Main Power House fuel spill site, Casey Station, Windmill Islands, Antarctic During the 2005/06 summer, a permeable bio-reactive barrier was designed and built to intercept the migrating fuel plume below the MPH and remediate water through the adsorption of hydrocarbons and delivery of nutrients to enhance microbial degradation. The PRB has been monitored (material and water sampling) each field season since installation. Barrier Design The PRB was of a “funnel and gate” design. The funnel was comprised of a high-density polyethylene (HDPE) impervious barrier membrane, with high hydraulic drainage material emplaced in front, directing groundwater into the treatment area (i.e. the gate). To assist in the transfer of migrating water to the reactive zone the wings had a gradient of 1:20. The treatment gate also had drainage material in the front to assist in the even distribution of groundwater across the face of the treatment zone. The reactive barrier gate comprised of five modified Australian Antarctic Division cage pellets, with the dimensions of 1.8 × 1.1 × 0.75 m. To separate each of the treatment cells a 2 mm galvanised steel sheet was placed between each cage. 400 micron nylon mesh was stapled to wooden end frames, and placed at the entry and exit of each cage to retain granular material and allow flow through the cells. 40 stainless steel 1⁄4” multiports (MP001 to MP040) were used to collect water samples at four depths, 700, 500, 300 and 100 mm below ground surface. Holes were also cut in the mesh alongside each of the multiports to allow coring of the material. In order to ensure thawing of the barrier prior to the surrounding area, three lengths of 118 m heat trace was wound on the underside of 50 mm square mesh and placed at 0.2, 0.4 and 0.6 meters below ground surface, each depth was independently controlled. 100 mm Styrofoam insulation was placed on the ends and 200 mm insulation beneath the c a b ± 0 2.5 5 7.5 10 Kilometres